HPA4 Review - Herb Reichert, Stereophile
HPA4 - "Satisfied my Engineering Mind and my Audiophile Lust"
"While removing the Benchmark HPA4 headphone amp, I noticed three things. First, I noticed that the amp had shipped from Syracuse, NY, where it was made. Second, one whole side of the box said "Benchmark. . . the measure of excellence!™" As I cut the clear tape with my boxcutter, I noticed the "THX Technology" logo printed on it and wondered why it was there."
"After admiring the black, 0.5"-thick, brushed-aluminum side panels, I looked at the HPA4's 0.25"-thick brushed aluminum front panel. The first thing I noticed was a 3.5" Color TFT touchscreen and thought, "I hope that screen has a dimmer." (It does.)"
"Looking at the chassis' back, it finally hit me. This thing is not just a headphone amp; it has four (!) line-level inputs: two unbalanced (RCA) and two balanced (XLR)."
"Then I peeked again at the instruction manual..."
The HPA4 is not just a "Reference Stereo Headphone Amplifier"; it is also a "Reference Line Amplifier" with "Relay Gain and Input Control."
"I didn't know what that last thing was, so I checked Benchmark's website and consulted via email with John Siau, Benchmark's vice president and chief engineer."
Relay-Controlled Gain
"Siau explained, "The Benchmark attenuator is actually a fully balanced relay-controlled gain stage. It applies up to 15 dB of gain or up to 127.5 dB of attenuation for a total range of 142.5 dB. There are 286 volume control steps in precise 0.5 dB increments. Of these, 256 are mapped to the user volume control. The remaining 30 steps are reserved for the balance control and for the input boost and cut functions that allow ... level matching of the four analog inputs. When this is set properly, the user can switch between sources without experiencing a change in volume level.""
Listening with Loudspeakers
"I replaced the hybrid (transformer-tube-JFET) Rogue Audio RP-7 line-level preamplifier with the Benchmark HPA4."
"Digital came from my reference HoloAudio May (Level 3) DAC feeding the balanced inputs of the HPA4. The Benchmark's 30 ohm output impedance fed the 33k ohm input impedance (via unbalanced Cardas Clear Cygnus) of a Parasound A21+ stereo amplifier powering Harbeth M30.2 monitors."
"During my first day of HPA4 listening, I noticed that every digital and analog recording was sounding curiously similar. They all sounded cleaner, better sorted, and more macrodynamic than they had with the Rogue, but strangely, compared to the RP-7, hall resonances and piano note reverb tails seemed shorter to me."
"The illusion of a sound space was enormous, but the HPA4's "enormous" sound space was different: images of performers inside the illusion appeared more distinctly outlined and concrete than I routinely observe with the Rogue. This sense of image concreteness appeared to be caused by, or enhanced by, the fact that the "empty spaces" surrounding these instrument and performer images were now the most air-free, glare-free, nonrefractive environs I have encountered while listening to home audio."
"The HPA4's sharp-focus specificity is something I associate with recording studio sound but almost never encounter in home systems."
THX-888 Headphone Amplifier
"The THX-888 headphone amplifier board "is a unity gain (current) amplifier with feedforward error correction." Feedforward error correction is also used in the AHB2 power amplifier."
"According to Benchmark's website, the HPA4 can deliver up to 11.9V RMS into 300 ohms and 6W into 16 ohms."
"The THX-888 headphone amplifier board in the HPA4 is manufactured by Benchmark under license from THX."
Driving HiFiMan Susvara Headphones
"With most headphone amplifiers, the tires go flat trying to drive HiFiMan's Susvara open-backed planar-magnetic circumaural headphones. The Susvara's low (83dB/mW) sensitivity and flat 60 ohm impedance need at least a few watts, probably a third of an amp, and maybe 7V, plus 15–20dB gain, to play effortlessly and sing with their clearest voice."
"Listening with the HPA4 and Susvara—I used the HPA4's balanced outputs for all my Susvara listening—and playing the full hour of Horowitz in Moscow (16/44.1 FLAC, Deutsche Grammophone/Qobuz) was the first full-length unmitigated musical pleasure I achieved with the HPA4."
"On this recording, with the HPA4, the notes from the master's piano were displayed with a weighty force and overtly pacey momentum that showed me more hammers and less pedal."
"The Benchmark-Susvara pairing moved the performances right along, emphasizing the authority of Horowitz's execution."
"After my HPA4-Horowitz experience, I had a feeling the Benchmark's absolute clarity coupled to the Susvara's legendary resolving powers would finally show me what the album's producers heard."
Powering Abyss TC Headphones
"Sticking with planar-magnetics but moving up the sensitivity ladder (to 88dB/mW), I again played Tango: Zero Hour, listening this time with the JPS Labs Abyss AB-1266 Phi TCs."
"Ultimately, the Benchmark-Abyss combo really clicked for me. It gave me a fresh, intriguing look at my most familiar recordings."
"The HPA4 exhibited no difficulty driving low-sensitivity, low-impedance planar magnetics."
Listening to ZMF Vérité Dynamic Headphones
"Next, I wanted to see how the THX 888 would fancy the 99dB/mW-sensitive, 300 ohm ZMF Vérité closed-backs."
"If you are considering buying or already own an HPA4, I recommend you audition the Zach Mehrbach–designed Vérité closed-backs. They were my favorite music-listening headphone with the HPA4."
Driving Focal Stellia Headphones
"The ZMF Vérité and the Focal Stellia are my references in the closed-back category."
"Of all the headphones in this test group, the 35 ohm, 106dB/mW Stellia present the easiest-to-drive load."
"Like high-quality, high-sensitivity floor speakers, the natural ease with which the "sound of music" flows out of them is the main reason I keep the Stellia in my daily-driver desktop system."
"The Stellia's ease of flow was not diminished while being driven by the Benchmark HPA4."
"Who would have imagined?"
"My romantic-dreamer mind adapted surprisingly well to the Benchmark HPA4's presentation."
"The more I used the HPA4 to drive high-resolution headphones, the more comfortable I felt with its precise, pro-audio recording-studio aesthetic."
"Spending a month with the HPA4 forced this old triode-tube lover to first acknowledge, then accept, and finally enjoy a new type of engagement, one that satisfied my engineering mind and my audiophile lust to look and listen into the hidden nooks and distant corners of every recording. Thank you, Benchmark."
- Herb Reichert, Stereophile
Also in Reviews
AHB2 Review - Constantine Soo, Dagogo
"The AHB2 bridgeable stereo amplifier ... was the topic of a recent discussion between American electrostatic panel speaker manufacturer Sound Lab’s president, Dr. Roger West, and me."
"In our discussion, he related his highly positive experience in driving even his largest, $55k Majestic 945 panels with the $7,000 pair of Benchmark Media AHB2 monoblocks, along with the $3,050 LA4 Preamplifier and factory XLR cables."
"Dr. West described the AHB2 as a class AB design using “feed-forward distortion reduction [thus removing] any possibility of pushing the margin of safety of a standard feedback loop, used in most amplifiers, into an unstable oscillatory mode.”"
"He further shared with me that “this is of most concern on powerful musical transients. The distortion of the amplifier in the balanced mode is astonishingly low even at just below the clipping level of 380 watts.”"
"The prospect of the AHB2’s specified distortion level of 0.00015% or lower when at full volume is comical at first glance, but upon actual audition the impact of the achievement is very audible from medium-high listening levels and upward."
"It was unlike any other sub-$20,000 amplifier I have auditioned."
"My audition of the Benchmark Media AHB2 amplifiers underscores the reason Dr. West is so taken by it, and confirms the design is best described as a watershed moment in the high-end audio industry."
- Constantine Soo, Dagogo
DAC3 Review - Jerry Del Colliano
"Benchmark is a stalwart brand in pro audio, but has carved out a very respectable niche in the audiophile world with their diminutive but powerful components."
"The audiophile world sometimes looks to the professional audio world for enlightenment, especially on the digital side of things, and Benchmark Media is one of the companies that we put high on a pedestal."
"They are hardcore digital engineers freezing their asses off in upstate New York as they come up with some pretty innovative ways to get your varied digital sources sounding as much like the master tape as possible. Thank you for your service, gentlemen."
"If you really want to hear what your music sounds like in today’s streaming-driven world, this might just be the DAC that you need to test out."
- Jerry Del Colliano, Future Audiophile
DAC3 & AHB2 - System Review, Trevor Butler, The-Ear.net
"I began with the DAC3 HGC and AHB2 powering the glorious Morel Avyra 633 three-way floorstanders."
"This pairing created a full-bodied sound which brought the recording to life."
"Notable from the off was the bass from the DAC3 HGC and AHB2."
"Wow! It was deep, tight and conveyed a real feeling that the electronics were in charge of the transducers."
"Involuntary foot-tapping confirmed the timing ability and the overall presentation was spot-on, the Benchmark electronics created a fluent sound across a vivid soundstage; performers evident both tonally and spatially in an easy-to-believe presentation that brought the performance close."
"The Benchmark’s ability to retrieve deep-down detail and display it so well across the soundstage, with accurate positioning and convincing layering, made for a glorious re-creation of the recordings."
"To my mind the AHB2 is an amplifier with no obvious characteristics of its own: the level of transparency is sublime."
"Above all, the improved transient response performance stood out in a presentation that was not only lively but incredibly fast and revealing. The attack and decay displayed was awesome and not something I expect at this price point."
"The Benchmark DAC3 HGC and AHB2 are cracking products, sonically superior to a lot that’s available and well priced."
"They are superbly designed and built to an extremely high standard."
- Trevor Butler, the-ear.net